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Updated: Jul 18, 2026

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Published on: November 18, 2022
Exploring the physical phase behavior of Ulva polysaccharide and soybean isolate protein complexes: the effects of pH
Kaixuan Bu1, Wenqin Chu1, Xianyu Li2
1College of Food Science and Engineering, Ocean University of China, No.1299, Sansha Road, Qingdao, Shandong Province, 266404, PR China.
Abstract:
The phase behavior of protein and polysaccharide mixed systems is crucial for investigating the formation of macromolecular gels. This manuscript examined the interactions between soy protein isolate (SPI) and Ulva clathrata polysaccharides (UCP) under varying pH and calcium ion concentrations, elucidating the underlying mechanisms. State diagrams constructed by the biopolymer composite system provided an intuitive visualization of the phase behavior. As the pH increased, electrostatic repulsion intensified, leading to a stable turbid system in the SPI-UCP complexes. Gaussian fitting analysis revealed that at pH 9.0, intermolecular hydrogen bonds dominated the hydrogen bonding interactions. When the calcium ion concentration approached the critical boundary (200 mM), the SPI-UCP hydrogel exhibited optimal gel hardness, storage modulus, and a dense, uniform pore structure. However, excessive Ca2+ promoted uncontrolled aggregation and salting-out effects, which impaired network uniformity and reduced effective cross-link density. Comprehensive analysis indicated that the interactions between SPI and UCP involved hydrogen bonding, electrostatic forces, hydrophobic interactions, and Ca2+ bridging. These findings provided novel insights into the interplay between SPI and UCP, offering a new perspective for modulating the gelation properties of UCP.
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